Overcoming resistance to EGFR tyrosine kinase inhibitors in lung cancer, focusing on non-T790M mechanisms

DUSP5 regulated by YTHDF1-mediated m6A modification promotes epithelial-mesenchymal transition and EGFR-TKI resistance via the TGF-β/Smad signaling pathway in lung adenocarcinoma

BACKGROUND

Lung adenocarcinoma (LUAD) patients have a dismal survival rate because of cancer metastasis and drug resistance. The study aims to identify the genes that concurrently modulate EMT, metastasis and EGFR-TKI resistance, and to investigate the underlying regulatory mechanisms.

METHODS

Cox regression and Kaplan-Meier analyses were applied to identify prognostic oncogenes in LUAD. Gene set enrichment analysis (GSEA) was used to indicate the biological functions of the gene. Wound-healing and Transwell assays were used to detect migratory and invasive ability. EGFR-TKI sensitivity was evaluated by assessing the proliferation, clonogenic survival and metastatic capability of cancer cells with treatment with gefitinib. Methylated RNA immunoprecipitation (MeRIP) and RNA immunoprecipitation (RIP) analyses established the level of m6A modification present on the target gene and the protein's capability to interact with RNA, respectively. Single-sample gene set enrichment (ssGSEA) algorithm used to investigate levels of immune cell infiltration.

RESULTS

Our study identified dual-specificity phosphatase 5 (DUSP5) as a novel and powerful predictor of adverse outcomes for LUAD by using public datasets. Functional enrichment analysis found that DUSP5 was positively enriched in EMT and transforming growth factor-beta (TGF-β) signaling pathway, a prevailing pathway involved in the induction of EMT. As expected, DUSP5 knockdown suppressed EMT via inhibiting the canonical TGF-β/Smad signaling pathway in in vitro experiments. Consistently, knockdown of DUSP5 was first found to inhibit migratory ability and invasiveness of LUAD cells in in vitro and prevent lung metastasis in in vivo. DUSP5 knockdown re-sensitized gefitinib-resistant LUAD cells to gefitinib, accompanying reversion of EMT progress. In LUAD tissue samples, we found 14 cytosine-phosphate-guanine (CpG) sites of DUSP5 that were negatively associated with DUSP5 gene expression. Importantly, 5'Azacytidine (AZA), an FDA-approved DNA methyltransferase inhibitor, restored DUSP5 expression. Moreover, RIP experiments confirmed that YTH N6-methyladenosine RNA binding protein 1 (YTHDF1), a m6A reader protein, could bind DUSP5 mRNA. YTHDF1 promoted DUSP5 expression and the malignant phenotype of LUAD cells. In addition, the DUSP5-derived genomic model revealed the two clusters with distinguishable immune features and tumor mutational burden (TMB).

CONCLUSIONS

Briefly, our study discovered DUSP5 which was regulated by epigenetic modification, might be a potential therapeutic target, especially in LUAD patients with acquired EGFR-TKI resistance.

Domain-specific p53 mutants activate EGFR by distinct mechanisms exposing tissue-independent therapeutic vulnerabilities

Mis-sense mutations affecting TP53 promote carcinogenesis both by inactivating tumor suppression, and by conferring pro-carcinogenic activities. We report here that p53 DNA-binding domain (DBD) and transactivation domain (TAD) mis-sense mutants unexpectedly activate pro-carcinogenic epidermal growth factor receptor (EGFR) signaling via distinct, previously unrecognized molecular mechanisms. DBD- and TAD-specific TP53 mutants exhibited different cellular localization and induced distinct gene expression profiles. In multiple tissues, EGFR is stabilized by TAD and DBD mutants in the cytosolic and nuclear compartments respectively. TAD mutants promote EGFR-mediated signaling by enhancing EGFR interaction with AKT via DDX31 in the cytosol. Conversely, DBD mutants maintain EGFR activity in the nucleus, by blocking EGFR interaction with the phosphatase SHP1, triggering c-Myc and Cyclin D1 upregulation. Our findings suggest that p53 mutants carrying gain-of-function, mis-sense mutations affecting two different domains form new protein complexes that promote carcinogenesis by enhancing EGFR signaling via distinctive mechanisms, exposing clinically relevant therapeutic vulnerabilities.

Sensitive detection of T790M mutations in lung cancer biopsies using a PCR-based lateral flow assay

T790 M point mutations in EGFR exon 20 are regarded as the most common cause of resistance to epidermal growth factor receptor tyrosine kinase inhibitor treatment. In this study, a PCR-based lateral flow assay (PCR-LFA) was developed to detect T790 M mutations in human genomic DNA. Detection sensitivity was determined using DNA at different mutant to wild-type ratios. The limit of detection of mutant alleles was 15 copies per reaction. The sensitivity of detection of these mutations in 40 formalin-fixed paraffin-embedded tissue biopsies from non-small cell lung cancer patients was analyzed using PCR-LFA and amplification refractory mutation system (ARMS) PCR. Our assay provided the same information as ARMS PCR for 95% (38/40) of the samples. T790 M mutations were detected in 15 (37.5%) and 13 samples using our assay and ARMS PCR, respectively. Droplet digital PCR confirmed the presence of T790 M mutations in the two discordant samples. These results indicate that PCR-LFA is more sensitive than ARMS PCR for clinical screening of these mutations.

Effectiveness of alectinib and osimertinib in a brain metastasized lung adenocarcinoma patient with concurrent EGFR mutations and DCTN1‐ALK fusion

The echinoderm microtubule associated protein‐like 4 gene (EML4) encodes the predominant anaplastic lymphoma kinase (ALK) fusion partner in non‐small‐cell lung cancer (NSCLC); however, the dynactin subunit 1 (DCTN1)‐ALK rearrangement is extremely rare. The co‐occurrence of primary epidermal growth factor receptor (EGFR) T790M mutation with EGFR exon 19 deletion (del) in patients with NSCLC is uncommon. Here we report a female lung adenocarcinoma patient with brain metastases and possible coexistence of primary EGFR T790M mutation/EGFR exon 19 del/DCTN1‐ALK translocation. The patient received multiline treatment including chemotherapy, antivascular, and targeted therapies. To overcome developed resistance to chemotherapy or targeted therapy to prolong overall survival, the patient's circulating tumor DNA (ctDNA) was dynamically monitored. The patient responded to successive osimertinib and alectinib treatment, and alectinib achieved a nearly complete response for lung and brain lesions after she acquired osimertinib resistance. Furthermore, we summarize 22 published cases of patients with lung adenocarcinoma with concurrent EGFR mutation and ALK rearrangement, including details of clinical characteristics, natural history, and pertinent therapy of this uncommon tumor subtype. This literature review shows that EGFR inhibition was an indispensable aspect of the treatment of patients with EGFR/ALK co‐alterations in the pre‐alectinib era and that ALK inhibition with crizotinib did not show more eye‐catching therapeutic results. Considering the effectiveness achieved by alectinib, this case study provides a new perspective for the treatment of lung cancer brain metastasis patients with concurrent EGFR/ALK mutations.

Multiplexed electrokinetic sensor for detection and therapy monitoring of extracellular vesicles from liquid biopsies of non-small-cell lung cancer patients

Liquid biopsies based on extracellular vesicles (EVs) represent a promising tool for treatment monitoring of tumors, including non-small-cell lung cancers (NSCLC). In this study, we report on a multiplexed electrokinetic sensor for surface protein profiling of EVs from clinical samples. The method detects the difference in the streaming current generated by EV binding to the surface of a functionalized microcapillary, thereby estimating the expression level of a marker. Using multiple microchannels functionalized with different antibodies in a parallel fluidic connection, we first demonstrate the capacity for simultaneous detection of multiple surface markers in small EVs (sEVs) from NSCLC cells. To investigate the prospects of liquid biopsies based on EVs, we then apply the method to profile sEVs isolated from the pleural effusion (PE) fluids of five NSCLC patients with different genomic alterations (ALK, KRAS or EGFR) and applied treatments (chemotherapy, EGFR- or ALK-tyrosine kinase inhibitors). The vesicles were targeted against CD9, as well as EGFR and PD-L1, two treatment targets in NSCLC. The electrokinetic signals show detection of these markers on sEVs, highlighting distinct interpatient differences, e.g., increased EGFR levels in sEVs from a patient with EGFR mutation as compared to an ALK-fusion one. The sensors also detect differences in PD-L1 expressions. The analysis of sEVs from a patient prior and post ALK-TKI crizotinib treatment reveals significant increases in the expressions of some markers (EGFR and PD-L1). These results hold promise for the application of the method for tumor treatment monitoring based on sEVs from patient liquid biopsies.

Antitumour immunity regulated by aberrant ERBB family signalling

Aberrant signalling of ERBB family members plays an important role in tumorigenesis and in the escape from antitumour immunity in multiple malignancies. Molecular-targeted agents against these signalling pathways exhibit robust clinical efficacy, but patients inevitably experience acquired resistance to these molecular-targeted therapies. Although cancer immunotherapies, including immune checkpoint inhibitors (ICIs), have shown durable antitumour response in a subset of the treated patients in multiple cancer types, clinical efficacy is limited in cancers harbouring activating gene alterations of ERBB family members. In particular, ICI treatment of patients with non-small cell lung cancers with epidermal growth factor receptor (EGFR) alterations and breast cancers with HER2 alterations failed to show clinical benefits, suggesting that EGFR and HER2 signalling may have an essential role in inhibiting antitumour immune responses. Here, we discuss the mechanisms by which the signalling of ERBB family members affects not only autonomous cancer hallmarks, such as uncontrolled cell proliferation, but also antitumour immune responses in the tumour microenvironment and the potential application of immune-genome precision medicine into immunotherapy and molecular-targeted therapy focusing on the signalling of ERBB family members.

2020 Innovation-Based Optimism for Lung Cancer Outcomes

Lung cancer is the leading cause of cancer death in both males and females in the U.S. and worldwide. Owing to advances in prevention, screening/early detection, and therapy, lung cancer mortality rates are decreasing and survival rates are increasing. These innovations are based on scientific discoveries in imaging, diagnostics, genomics, molecular therapy, and immunotherapy. Outcomes have improved in all histologies and stages. This review provides information on the clinical implications of these innovations that are practical for the practicing physicians, especially oncologists of all specialities who diagnose and treat patients with lung cancer. IMPLICATIONS FOR PRACTICE: Lung cancer survival rates have improved because of new prevention, screening, and therapy methods. This work provides a review of current standards for each of these areas, including targeted and immunotherapies. Treatment recommendations are provided for all stages of lung cancer.

EPHA2 Interacts with DNA-PKcs in Cell Nucleus and Controls Ionizing Radiation Responses in Non-Small Cell Lung Cancer Cells

Ephrin (EFN)/ Erythropoietin-producing human hepatocellular receptors (Eph) signaling has earlier been reported to regulate non-small cell lung cancer (NSCLC) cell survival and cell death as well as invasion and migration. Here, the role of Ephrin type-A receptor 2 (EphA2) on the DNA damage response (DDR) signaling and ionizing radiation (IR) cellular effect was studied in NSCLC cells. Silencing of EphA2 resulted in IR sensitization, with increased activation of caspase-3, PARP-1 cleavage and reduced clonogenic survival. Profiling of EphA2 expression in a NSCLC cell line panel showed a correlation to an IR refractory phenotype. EphA2 was found to be transiently and rapidly phosphorylated at Ser897 in response to IR, which was paralleled with the activation of ribosomal protein S6 kinase (RSK). Using cell fractionation, a transient increase in both total and pSer897 EphA2 in the nuclear fraction in response to IR was revealed. By immunoprecipitation and LC-MS/MS analysis of EphA2 complexes, nuclear localized EphA2 was found in a complex with DNA-PK_cs. Such complex formation rapidly increased after IR but returned back to basal level within an hour. Targeting EphA2 with siRNA or by treatment with EFNA1 ligand partly reduced phosphorylation of DNA-PK_cs at S2056 at early time points after IR. Thus, we report that EphA2 interacts with DNA-PK_cs in the cell nucleus suggesting a novel mechanism involving the EphA2 receptor in DDR signaling and IR responsiveness.

Detection of Tumor-Associated Membrane Receptors on Extracellular Vesicles from Non-Small Cell Lung Cancer Patients via Immuno-PCR

Simple Summary

Lung cancer is often detected at late stages when metastases are present and the genomic make-ups of the tumors are heterogeneous. Analyses of genomic alterations in non-small-cell lung cancer (NSCLC) have revealed mutated tumor-associated membrane receptors and fusion proteins, which can be targeted via tyrosine kinase inhibitors (TKIs). TKIs initially often have a good effect, but a fraction of the tumor lesions may develop resistance through additional mutations in the targeted kinases or by increased expression/function of other membrane receptors. Detection of TKI-bypassing mechanisms is difficult in tissue biopsies as these analyze only a subpart of tumors or lesions. Liquid biopsies based on tumor-secreted small extracellular vesicles (sEVs) into body fluids can assess tumor heterogeneity. We present an immuno-PCR method for the detection of the epidermal growth factor receptor (EGFR), the human epidermal growth factor receptor 2 (HER2), and the insulin-like growth factor 1 receptor (IGF-1R) on sEVs. Initial investigations of sEVs from EGFR-mutant NSCLC tumor cells or pleural effusion (PE) fluid from patients with NSCLC or benign diseases showed different protein profiles for individual sEV samples. Further development of the immuno-PCR could complement DNA/mRNA-based assays detecting kinase mutations to allow longitudinal treatment monitoring of diverse TKI-bypassing mechanisms.

Abstract

Precision cancer medicine for non-small-cell lung cancer (NSCLC) has increased patient survival. Nevertheless, targeted agents towards tumor-associated membrane receptors only result in partial remission for a limited time, calling for approaches which allow longitudinal treatment monitoring. Rebiopsy of tumors in the lung is challenging, and metastatic lesions may have heterogeneous signaling. One way ahead is to use liquid biopsies such as circulating tumor DNA or small extracellular vesicles (sEVs) secreted by the tumor into blood or other body fluids. Herein, an immuno-PCR-based detection of the tumor-associated membrane receptors EGFR, HER2, and IGF-1R on CD9-positive sEVs from NSCLC cells and pleural effusion fluid (PE) of NSCLC patients is developed utilizing DNA conjugates of antibody mimetics and affibodies, as detection agents. Results on sEVs purified from culture media of NSCLC cells treated with anti-EGFR siRNA, showed that the reduction of EGFR expression can be detected via immuno-PCR. Protein profiling of sEVs from NSCLC patient PE samples revealed the capacity to monitor EGFR, HER2, and IGF-1R with the immuno-PCR method. We detected a significantly higher EGFR level in sEVs derived from a PE sample of a patient with an EGFR-driven NSCLC adenocarcinoma than in sEVs from PE samples of non-EGFR driven adenocarcinoma patients or in samples from patients with benign lung disease. In summary, we have developed a diagnostic method for sEVs in liquid biopsies of cancer patients which may be used for longitudinal treatment monitoring to detect emerging bypassing resistance mechanisms in a noninvasive way.

Efficacy of epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) combined with bevacizumab for advanced non-squamous non-small-cell lung cancer patients with gradual progression on EGFR-TKI treatment: A cohort study

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) significantly improve outcomes of patients with EGFR-mutated non-small-cell lung cancer (NSCLC). However, acquired resistance inevitably emerges and remains a major challenge. The present study aimed to evaluate the efficacy of EGFR-TKIs plus bevacizumab in advanced non-squamous NSCLC patients with gradual progression on EGFR-TKIs.Advanced non-squamous EGFR-mutated NSCLC patients with gradual progression on EGFR-TKIs were administered bevacizumab while EGFR-TKIs were continued until disease progression occurred. Tumor lesions were assessed, and blood samples were collected at the start of the combination treatment and every 6 weeks until disease progression.Among the 15 included patients, there were no grade 3 or higher adverse events (AEs). Partial response (PR) and stable disease (SD) were achieved in 1 and 13 patients, respectively, with an objective response rate (ORR) of 6.7% and a disease control rate (DCR) of 93.3%. The median progression-free survival 2 (PFS2), defined as the time from the initiation of combination treatment to disease progression, was 5.0 (95% confidence interval [CI]: 4.0-6.0) months. Additionally, Spearman correlation analysis revealed that PFS2 was positively correlated with the serum vascular endothelial growth factor (VEGF) level at baseline (r = 0.7212, P = .0234). Patients with high baseline serum VEGF levels showed a better median PFS2 than those with low baseline serum VEGF levels (5.5 months vs 3.6 months, P = .0333).EGFR-TKIs plus bevacizumab led to a durable prolongation of PFS in non-squamous NSCLC patients with gradual progression on EGFR-TKIs. This therapeutic regimen was well tolerated and could be a promising strategy for these patients. Serum VEGF could be a potential biomarker to predict a subset of patients who are likely to benefit from EGFR-TKIs combined with bevacizumab.

All-trans retinoic acid reduces cancer stem cell-like cell-mediated resistance to gefitinib in NSCLC adenocarcinoma cells

Background

The enrichment of cancer stem cell-like cells (CSCs) has been considered to be responsible for tumor progression after an initial response to epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (EGFR-TKIs) in patients with non-small cell lung adenocarcinoma (NSCLC/ADC). CSCs with ALDH1A1^bright /CD44^high expression contribute to the TKIs resistance in NSCLC/ADC cells. All-trans retinoic acid (ATRA) has been shown to be a potential targeted therapy against CSCs due to its ability to inhibit ALDH1A1 activity. We therefore investigated whether ATRA could circumvent the resistance to improve the response to gefitinib in NSCLC/ADC cells.

Methods

Treatment of NSCLC/ADC A549 and H1650 cells with gefitinib enriched the gefitinib surviving cells (GSCs). The expression of ALDH1A1 and CD44 and the IC50 values for gefitinib were determined by flow cytometry (FCM) and crystal violet assay in GSCs and ATRA-treated GSCs, respectively. Using DEAB as the positive control, direct inhibitory effect of ATRA on ALDH1A1 activity was determined by ALDEFLUOR assay,

Results

GSCs showed higher expression of ALDH1A1 and CD44 and IC50 values for gefitinib than their respective parental cells, suggesting that gefitinib can lead to propagation of CSC-enriched gefitinib-resistant cells. Treatment with ATRA was found to significantly reduce the increased expression of ALDH1A1 and CD44 and the IC50 values for gefitinib in A549GSC and H1650GSC cells, and ATRA could directly inhibit active ALDH1A1 as compared to DEAB.

Conclusion

Our findings suggest that combination treatment with ATRA prevents gefitinib-induced enrichment of ALDH1A1^bright/CD44^high CSCs and enhances gefitinib-induced growth inhibition of NSCLC/ADC cells.

Diagnostic test accuracy of droplet digital PCR for the detection of EGFR mutation (T790M) in plasma: Systematic review and meta-analysis

BACKGROUND

T790M mutation was a primary lead cause in the acquired resistance to EGFR-TKIs confirmed in earlier studies. Since the shortcomings of tumor tissue detection are well known, the liquid biopsy is more appropriate to track T790M status. We assessed the accuracy and clinical significance of the droplet digital PCR (ddPCR) detection of T790M mutation in plasma.

METHODS

We retrieved PubMed, Embase, Cochrane, and Web of science with no limitation of language and publication year. Summary sensitivity and specificity, positive likelihood ratio (PLR), negative likelihood ratio (NLR) and diagnostic odds ratio of detection of EGFR T790M status were calculated from extracted data from included articles. The summary receiver operating curve (SROC), diagnostic odds ratio (DOR), and the area under the summary receiver operating curve (AUC) was used to assess the overall diagnostic accuracy. I² and meta-regression were used to evaluate heterogeneity and the source of heterogeneity, respectively.

RESULT

We identified 15 studies in the total search of 1364 reports, including 427 paired tissue and plasma samples. The pooled sensitivity and the pooled specificity were 0.68 (95% CI 0.61-0.75) and 0.85 (95% CI 0.75-0.91) by the bivariate model, respectively. The AUC and the pooled DOR were 0.78 (95% CI 0.74-0.81) and 12 (95% CI 7-22), respectively. None of the cofactors could account for the heterogeneity.

CONCLUSION

The plasma analysis is of a promising performance to screen EGFR-T790M mutation status by ddPCR.

Discovery of an Oleanolic Acid/Hederagenin-Nitric Oxide Donor Hybrid as an EGFR Tyrosine Kinase Inhibitor for Non-Small-Cell Lung Cancer

Natural triterpenoids, such as oleanolic acid (OA) and hederagenin, display anti-lung cancer effects, and nitric oxide (NO) is associated with some oncogenic signaling pathways. Accordingly, 17 OA/hederagenin-NO donor hybrids were designed, synthesized, and evaluated against tumor cells. The most potent compound, 13, significantly inhibited the proliferation of five tumor cell lines (IC₅₀ 4.6-5.2 μM), while hederagenin inhibited the growth of only A549 tumor cells (IC₅₀ > 10 μM). Furthermore, compound 13 showed stronger inhibitory effects on EGFR-LTC kinase activity (IC₅₀ 0.01 μM) than hederagenin (IC₅₀ > 20 μM) and inhibited the proliferation of gefitinib-resistant H1975 (IC₅₀ 8.1 μM) and osimertinib-resistant H1975-LTC (IC₅₀ 7.6 μM) non-small-cell lung cancer (NSCLC) cells. Moreover, compound 13 produced the most NO in H1975 tumor cells, which indicated that NO may play a synergistic role. Collectively, compound 13, a novel hederagenin-NO donor hybrid with a different chemical structure from those of the current FDA-approved EGFR-targeted anti-NSCLC drugs, may be a promising lead compound for the treatment of NSCLC expressing gefitinib-resistant EGFR with a T790 M mutation or osimertinib-resistant EGFR-LTC with an L858R/T790M/C797S mutation. This work should shed light on the discovery of new anti-NSCLC drugs targeting EGFR from natural products.

Combination of EGFR-TKIs and chemotherapy in advanced EGFR mutated NSCLC: Review of the literature and future perspectives

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) improved clinical outcome compared to chemotherapy in EGFR mutated advanced non-small cell lung cancer (NSCLC) patients. Nonetheless, acquired resistance develops within 10-14 months and 20-30% of EGFR-mutated patients do not respond to EGFR-TKI. In order to delay or overcome acquired resistance to EGFR-TKIs, combination therapies of EGFR-TKIs with chemotherapy has been investigated with conflicting results. Early studies failed to show a survival benefit because of a lack of patient selection, but more recently clinical studies in EGFR mutated patients have shown promising results. This review summarizes preclinical and clinical studies of combination of EGFR-TKIs, including the third-generation TKI osimertinib, with chemotherapy in first- and second-line settings, using concurrent or intercalated treatment strategies. In the new era of third-generation EGFR-TKIs, new studies of this combination strategy are warranted.

Role of the dynamic tumor microenvironment in controversies regarding immune checkpoint inhibitors for the treatment of non-small cell lung cancer (NSCLC) with EGFR mutations

Immunotherapy has been incorporated into the first- and second-line treatment strategies for non-small cell lung cancer (NSCLC), profoundly ushering in a new treatment landscape. However, both adaptive signaling and oncogenic (epidermal growth factor receptor (EGFR)-driven) signaling may induce PD-L1 upregulation in NSCLC. Nevertheless, the superiority of immune checkpoint inhibitors (ICIs) in advanced EGFR-mutant NSCLC is only moderate. ICIs appear to be well tolerated, but clinical activity for some advanced EGFR-mutant NSCLC patients has only been observed in a small proportion of trials. Hence, there are still several open questions about PD-L1 axis inhibitors in patients with NSCLC whose tumors harbor EGFR mutations, such as the effect of EGFR tyrosine kinase inhibitors (TKIs) or EGFR mutations in the tumor microenvironment (TME). Finding the answers to these questions requires ongoing trials and preclinical studies to identify the mechanisms explaining this possible increased susceptibility and to identify prognostic molecular and clinical markers that may predict benefits with PD-1 axis inhibition in this specific NSCLC subpopulation. The presence of multiple mechanisms, including dynamic immune TME profiles, changes in PD-L1 expression and low tumor mutational burdens, may explain the conflicting data regarding the correlation between PD-L1 axis inhibitors and EGFR mutation status. We conducted a review of this currently controversial topic in an attempt to aid in the decision-making process.

Hsp90 inhibitors enhance the antitumoral effect of osimertinib in parental and osimertinib-resistant non-small cell lung cancer cell lines

Background

Osimertinib improve therapy for non-small cell lung cancer (NSCLC). However, invariable acquired resistance appears.

Methods

MTT assay was used to analyze cell viability. Protein expression and activation was detected by Western blotting. In addition, the effects of heat shock protein 90 (Hsp90) inhibitors and osimertinib were studied in colony formation assays.

Results

Our laboratory generated osimertinib resistant cell lines from PC9 cell line and overexpression or activation of several proteins was detected. Hsp90 inhibitors, ganetespib and luminespib, inhibited cell viability and colony formation in H1975, PC9 and PC9-derived osimertinib-resistant cell lines and combination of these inhibitors with osimertinib achieved to enhance this cell viability and colony formation inhibition. Luminespib downregulated the expression of the several proteins involved in osimertinib-resistance and the combination of this compound plus osimertinib caused an important decrease of expression of several of these proteins, such as Stat3, Yap, Akt, EGFR and Met. Osimertinib activated the phosphorylation of several membrane receptors and downstream molecules that was partially inhibited by luminespib. In addition, a lung cancer patient with an EGFR eon 20 mutation had a partial radiographic response to ganetespib.

Conclusions

Hsp90 inhibitors and osimertinib exhibits a good efficiency to inhibit cell viability, colony formation and inhibits expression and activation of proteins involved in osimertinib-resistance and may represent an effective strategy for NSCLC with intrinsic resistance to osimertinib inhibition.

Overcoming acquired resistance of gefitinib in lung cancer cells without T790M by AZD9291 or Twist1 knockdown in vitro and in vivo

The T790M mutation is recognized as a typical mechanism of acquired resistance to first generation of epithermal growth factor receptor-tyrosine kinase inhibitors (EGFR-TKIs) such as gefitinib in non-small cell lung cancer (NSCLC) patients who are commonly treated by third generation of EGFR-TKI AZD9291 (osimertinib). However, the therapeutic strategy for overcoming acquired resistance to EGFR-TKIs in NSCLC patients without T790M remains to be definitively determined. In the present study, gefitinib-resistant H1650 (H1650GR) or AZD9291-resistant H1975 (H1975AR) was generated by exposing NSCLC cell line H1650 or H1975 to progressively increased concentrations of gefitinib or AZD9291 over 11 months. The cytotoxic effects of gefitinib or AZD9291 in vitro were evaluated via the half maximal inhibitory concentrations (IC50s) determined by the MTT assay. IC50 of gefitinib in H1650GR (50.0 ± 3.0 µM) significantly increased compared with H1650 (31.0 ± 1.0 µM) (p < 0.05). Similarly, the IC50 of AZD9291 in H1975AR (10.3 ± 0.9 µM) significantly increased compared with H1975 (5.5 ± 0.6 µM) (p < 0.05). However, IC50 of AZD9291 on H1650GR (8.5 ± 0.5 µM) did not increase compared with H1650 (9.7 ± 0.7 µM). On the other hand, IC50 of AZD9291 on gefitinib-resistant A549 (A549GR established in our previous study) (12.7 ± 0.8 µM) was significantly increased compared with A549 (7.0 ± 1.0 µM) (p < 0.05). AZD9291 induced caspase 3/7 activation in A549, H1650, and H1650GR, but not in A549GR. Western blot analyses showed that p-Akt played a key role in determining the sensitivities of A549, A549GR, H1650, and H1650GR to gefitinib or AZD9291. Additionally, increased expression of Twist1 was observed in all cells with acquired EGFR-TKI resistance and knockdown of Twist1 by shRNA was found to significantly enhance the sensitivity of A549GR to gefitinib or AZD9291 via reversing epithelial-mesenchymal transition and downregulating p-Akt, but not of H1975AR to AZD9291. The enhanced cytotoxic effect of AZD9291 on A549GR by Twist1 knockdown in vitro was further validated by in vivo studies which showed that Twist1 knockdown could lead to significantly delayed tumor growth of A549GR xenograft with increased sensitivity to AZD9291 treatment in nude mice without any observed side toxic effects. In summary, our study demonstrated that the mechanisms of acquired resistance in different NSCLC cell lines treated by even the same EGFR-TKI might be quite different, which provide a rationale for adopting different therapeutic strategies for those NSCLC patients with acquired EGFR-TKI resistance based on different status of heterogeneous mutations.

Role of Cytomorphology in the Era of Liquid Biopsy

In the late stages of non-small cell lung cancer, the detection of sensitizing mutations of the epidermal growth factor receptor (EGFR) is mandatory to select patients' treatment with first- or second-generation tyrosine kinase inhibitors (TKIs). In patients showing progressive disease, the assessment of the EGFR exon 20 resistance point mutation p.T790M is required for third-generation TKI administration. However, molecular analysis does not capture all the different mechanisms of resistance against these molecules. A variety of morphological changes associated with acquired resistance have also been described. Since an altered morphology may be the only clue to acquired resistance, cytopathology still plays a relevant role in this setting. In this comprehensive review, we have focused on the relevance of squamous cell carcinoma, small cell lung cancer and large-cell neuroendocrine carcinoma transitions from adenocarcinoma resistant to TKIs.

APE1 stimulates EGFR-TKI resistance by activating Akt signaling through a redox-dependent mechanism in lung adenocarcinoma

Epidermal growth factor receptor tyrosine kinase inhibitors (EGFR-TKIs) have become the standard first-line treatment for advanced lung adenocarcinoma (LUAD) cancer patients with activating EGFR mutations. However, most patients show acquired resistance to EGFR-TKIs, thereby resulting in a modest overall survival benefit. Here, we found that expression level of APE1 was closely associated with TKI resistance in LUAD. Our clinical data show that level of APE1 was inversely correlated with progression-free survival rate and median time to progression in EGFR-mutated LUAD patients. Additionally, we observed increased expression of APE1 in TKI-resistant LUAD cell lines compared to their parental cell lines. Overexpression of APE1-protected TKI-sensitive LUAD cells from TKI-induced cell growth inhibition and cell death. In contrast, inhibition of APE1-enhanced TKI-induced apoptosis, cell growth inhibition and tumor growth inhibition in TKI-resistant LUAD. In addition, we identified that APE1 positively regulates Akt activation and APE1 overexpression-induced TKI resistance was attenuated by inhibition of Akt activity. Finally, we demonstrated that inhibition of the redox function of APE1 enhances the sensitivity of TKI-resistant LUAD cells to TKI treatment and inhibits Akt phosphorylation in TKI-resistant LUAD cells, but not by inhibition of the APE1 DNA repair function. Taken together, our data show that increased expression of APE1 significantly contributes to TKI resistance development in LUAD, and targeting APE1 may reverse acquired resistance of LUAD cells to TKI treatment. Additionally, our data show that APE1 regulates TKI resistance in LUAD cells by activating Akt signaling through a redox-dependent mechanism.

HER1-based vaccine: Simultaneous activation of humoral and cellular immune response

The human epidermal growth factor receptor 1 (HER1) is a tumor-associated antigen that has been validated as a clinical target for several passive, non-immune therapies currently approved for the treatment of epithelial tumors. HER1 is an oncogene that not only promotes tumor progression and survival, but also immune escape. Its overexpression in some epithelial malignancies has been correlated with a poor prognosis. We developed an approach to target HER1 by specific active immunotherapy, recognizing the extracellular domain of the receptor, using a combination of VSSP and Montanide ISA 51 as adjuvants. We summarize the results obtained with this vaccine in both the preclinical and clinical settings, emphasizing the importance of the induction of both humoral and cellular responses for the success of cancer vaccines as safe therapeutic alternatives for the treatment of cancer.

The diagnostic accuracy of circulating tumor DNA for the detection of EGFR-T790M mutation in NSCLC: a systematic review and meta-analysis

This pooled analysis aims at evaluating the diagnostic accuracy of circulating tumor (ct) DNA for the detection of EGFR-T790M mutation in NSCLC patients who progressed after EGFR-TKIs. Data from all published studies, reporting both sensitivity and specificity of plasma-based EGFR-T790M mutation testing by ctDNA were collected by searching in PubMed, Cochrane Library, American Society of Clinical Oncology, European Society of Medical Oncology and World Conference of Lung Cancer meeting proceedings. A total of twenty-one studies, with 1639 patients, were eligible. The pooled sensitivity of ctDNA analysis was 0.67 (95% CI: 0.64–0.70) and the pooled specificity was 0.80 (95% CI: 0.77–0.83). The pooled positive predictive value (PPV) was 0.85 (95% CI: 0.82–0.87) and the pooled negative predictive value (NPV) was 0.60 (95% CI: 0.56–0.63). The positive likelihood ratio (PLR) and negative likelihood ratio (NLR) were 2.67 (95% CI: 1.86–3.82) and 0.46 (95% CI: 0.38–0.54), respectively. The pooled diagnostic odds ratio (DOR) was 7.27 (4.39–12.05) and the area under the curve (AUC) of the summary receiver operating characteristics (sROC) curve was 0.77. The ctDNA analysis represents a promising, non-invasive approach to detect and monitor the T790M mutation status in NSCLC patients. Development of standardized methodologies and clinical validation are recommended.

Shikonin sensitizes wild‑type EGFR NSCLC cells to erlotinib and gefitinib therapy

As patients with non-small cell lung cancer (NSCLC) and wild-type epidermal growth factor receptor (EGFR) are resistant to treatment with erlotinib or gefitinib, potential chemosensitizers are required to potentiate wild-type EGFR NSCLC cells to erlotinib/gefitinib treatment. The present study reported that shikonin could sensitize the anticancer activity of erlotinib/gefitinib in wild-type EGFR NSCLC cells. Furthermore, shikonin could potentiate mitochondrial-mediated apoptosis induced by erlotinib/gefitinib in wild-type EGFR NSCLC cells. In addition, the present study demonstrated that shikonin could induce apoptosis by activating reactive oxygen species (ROS)-mediated endoplasmic reticulum (ER) stress, and that erlotinib/gefitinib may also induce ER stress in wild-type EGFR NSCLC cells; however, shikonin plus erlotinib/gefitinib was more effective in activating ER stress than either agent alone. This indicated that ROS-mediated ER stress may be associated with enhanced mitochondrial apoptosis induced by shikonin plus erlotinib/gefitinib. In addition, shikonin may promote the transition of cytoprotective ER stress-inducing EGFR-tyrosine kinase inhibitor tolerance to apoptosis-promoting ER stress. Furthermore, shikonin may enhance the anti-NSCLC activity of erlotinib/gefitinib in vivo. The data of the present study indicated that shikonin may be a potential sensitizer to enhance the anti-cancer efficacy of erlotinib/gefitinib in wild-type EGFR NSCLC cells resistant to erlotinib/gefitinib treatment.

A Combination of Approved Antibodies Overcomes Resistance of Lung Cancer to Osimertinib by Blocking Bypass Pathways

Purpose: Because of emergence of resistance to osimertinib, a third-generation EGFR tyrosine kinase inhibitor (TKI), no targeted treatments are available for patients with lung cancer who lose sensitivity due to new mutations or bypass mechanisms. We examined in animals and in vitro an alternative therapeutic approach making use of antibodies.Experimental Design: An osimertinib-sensitive animal model of lung cancer, which rapidly develops drug resistance, has been employed. To overcome compensatory hyperactivation of ERK, which we previously reported, an anti-EGFR antibody (cetuximab) was combined with other antibodies, as well as with a subtherapeutic dose of osimertinib, and cancer cell apoptosis was assayed.Results: Our animal studies identified a combination of three clinically approved drugs, cetuximab, trastuzumab (an anti-HER2 mAb), and osimertinib (low dose), as an effective and long-lasting treatment that is able to prevent onset of resistance to osimertinib. A continuous schedule of concurrent treatment was sufficient for effective tumor inhibition and for prevention of relapses. Studies employing cultured cells and analyses of tumor extracts indicated that the combination of two mAbs and a subtherapeutic TKI dose sorted EGFR and HER2 for degradation; cooperatively enhanced apoptosis; inhibited activation of ERK; and reduced abundance of several bypass proteins, namely MET, AXL, and HER3.Conclusions: Our in vitro assays and animal studies identified an effective combination of clinically approved drugs that might overcome resistance to irreversible TKIs in clinical settings. The results we present attribute the long-lasting effect of the drug combination to simultaneous blockade of several well-characterized mechanisms of drug resistance. Clin Cancer Res; 24(22); 5610-21. ©2018 AACR See related commentary by Fan and Yu, p. 5499.

Increased expression of miR-641 contributes to erlotinib resistance in non-small-cell lung cancer cells by targeting NF1

Epidermal growth receptor (EGFR)‐targeted tyrosine kinase inhibitors (TKIs) have emerged as first‐line drugs for advanced non‐small‐cell lung cancer (NSCLC) patients with EFGR mutations. However, most patients with NSCLC show acquired resistance to EGFR‐TKIs, and low expression of NF1 is a mechanism of EGFR‐TKI resistance in lung cancer. However, the mechanism by which NF1 is downregulated in EGFR‐TKI‐resistant NSCLC is unclear. Here, we found the increased expression of miR‐641 in NSCLC cells and human NSCLC samples with resistance to TKI compared to those with sensitive to TKI. In addition, our in vitro experiments show that overexpression of miR‐641 induces TKI resistance in NSCLC cells. Furthermore, we identified that miR‐641 activates ERK signaling by direct targeting of neurofibromatosis 1 (NF1) in NSCLC cells. Our data show that overexpression of NF1 or silencing of ERK can block miR‐641‐induced resistance of NSCLC cells to erlotinib treatment. Importantly, our animal experiments show that combination of miR‐641 inhibition and erlotinib treatment can significantly inhibit erlotinib‐resistant NSCLC growth, inhibit proliferation and induce apoptosis compared to single‐drug treatment. Our findings suggest that increased expression of miR‐641 significantly contributes to erlotinib resistance development in NSCLC cells through activating ERK signaling by targeting NF1 and that inhibition of miR‐641 may reverse acquired resistance of NSCLC cells to erlotinib treatment.

Combined therapy with epidermal growth factor receptor tyrosine kinase inhibitors for non-small cell lung cancer

INTRODUCTION

Epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (TKIs) have a pronounced clinical benefit for patients with advanced non-small cell lung cancer (NSCLC) positive for EGFR activating mutations. Such individuals inevitably develop resistance to these drugs, however, new treatment strategies to overcome such resistance are being actively pursued. The clinical benefit of EGFR-TKIs for patients with locally advanced NSCLC remains to be clarified. Areas covered: This review summarizes the recent progress in combination treatment with EGFR-TKIs and either chemotherapy or radiotherapy for patients with NSCLC positive for EGFR activating mutations. Expert commentary: Combination therapy with EGFR-TKIs and various other treatment options are under investigation in clinical studies. Although early studies failed to show a clinical benefit for such combination therapy because of a lack of patient selection, clinical studies with patient selection based on EGFR mutation status have shown promising results. Such combination therapy might eventually replace the current standard treatment for patients with NSCLC positive for EGFR activating mutations.